Spring Rate, rear

What spring rate are you using on your rear ST shock? What is your weight and riding style?

The reason I ask is because I'm getting conflicting information when I ask what spring rate is suggested as a starting point for my load. Springs are not cheap.

Lindemann said 625 for my situation. Then when I reported back that with the 625 spring the preload had to be almost 25mm he said an 800 pound spring is what is needed. No other supplier has ever suggested an 800.

With both bags loaded, wearing all my gear, and packed for a camping trip, my load is around 310 pounds. Some suppliers say I should use a 675 lb/inch spring rate. Some say 750, and one says 800 pound/inch.

Right now, with a 700 pound spring, and with the sag set to around 35mm, I need about 12mm of preload.

Comments are appreciated.

Well I am using the stock spring but with my weight [210 lb] I need to set to max preload for solo riding to achieve 35mm loaded sag.

You should give BCM a call. They keep notes on what works for all different bikes, which was very helpful when I had them swap out the rear spring on my ST4S.

Dan,
I have a 98 ST2. I weigh 200lbs and I often carry a passenger (she's not saying what she weighs!!!)
I had the same exact problem as you.
1. went to 625lb spring..still soft. BTW..the stock spring is 525lbs.
2. got a 800lb spring..perfect. Middle preload position- (solo) ,,,3 turns firmer (loaded, two-up, trackdays)
DO IT!!
Peter Kates at Computrack Boston sold me the spring and reported it was the stiffest one he's ever installed besides a 1k on his racebike. He also rebuilt my leaking shock.
Steve

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tricklidz1 &raquo;</TD></TR><TR><TD CLASS="quote"> I weigh 200lbs and I often carry a passenger (she's not saying what she weighs!!!)

...got a 800lb spring..perfect.</TD></TR></TABLE>

Thanks for the reply. So your total load is around 350 (200 + say, 150). Have you ever measured the free and loaded sag? When you say it's perfect, what do you mean?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DanST4 &raquo;</TD></TR><TR><TD CLASS="quote">

Thanks for the reply. So your total load is around 350 (200 + say, 150). Have you ever measured the free and loaded sag? When you say it's perfect, what do you mean?</TD></TR></TABLE>

Yes, at least 350...more when fully packed.
I've done much measuring of sag, etc, before I got the 800 lb spring..but since then, it works so well I just leave it alone.
I have about 35mm sag...solo with the preload in the middle setting. Then when I ride double I just adj. three clicks stiffer...(also 35 mm sag.) that leaves one ramp left on the collar.
I also adj. the rebound for each setting...I leave the comp. alone because I feel it doesn't make much difference. Remember though, that I had the damper rebuilt..so YMMV.
Steve

Well that sounds about right. I may go with the 800 pound spring. I have a Penske shock which I'll have to get revalved so that the rebound matches the stronger spring. Lindemann can easily do that when they change the spring.

800 sounded so darn high compared to what a lot of sources were telling me was "ballpark". Right now the 700 has too much preload, so the 800 might be the ticket.

I'm going to end up having a lot of springs on the shelf (right next to the 25 year old boxes of old Mikuni jets, and that box of old DynoJet needles...

THANKS for the info.

Have lindemann put on the Ti spring on your shock. dropped 3.5 lbs off my bike from the stock shock to Ti Penske.

I called Jim Lindemann and he can't yet get a Ti spring with a spring rate over 700. Lindemann and BCM both feel that the 800-pound spring rate is the one for my application, so the shock is on its way to Lindemann.

That's too bad about the Ti spring. My shock from them is excellent. I plan to send the forks there someday.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by foggy123 &raquo;</TD></TR><TR><TD CLASS="quote">I plan to send the forks there someday. </TD></TR></TABLE>

They did my forks too, and I think you're going to love that mod. With the correct springs and all their little tricks, the forks respond to irregularities like nothing I've ever experienced. I also had them do the TiN coating for longevity and reduced stiction.

The bike really feels planted. The forks absorb even the smallest bumps and give a smoother ride, yet when I hit a really big expansion joint they just suck it up. It's safer.

Well worth the money in my opinion.

Your stock spring rate is 9.2Kg/mm.....or 20.3lbs/mm which translates to about 515.2lbs/in.

At 315 lbs cruising weight, your preload should be set at 15.5mm. End of discussion.


If you want a custom spring rate, decide from there what you need for youself, instead of letting a bunch of Yahoo's speculate on what they think you need. Remember, it's your ass on the bike. Not theirs. Go to stiff, and you'll pay the price on a bumpy curve in the middle of nowhere.

Variables? Who needs them stinking variables?

Lindemann and BCM both feel that the 800-pound spring rate&gt;&gt;
Bunch of Yahoo's???
I think not.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tricklidz1 &raquo;</TD></TR><TR><TD CLASS="quote">Lindemann and BCM both feel that the 800-pound spring rate&gt;&gt;
Bunch of Yahoo's???
I think not. </TD></TR></TABLE>

Talked with Jim Lindemann yesterday. He swapped to the 800# spring and revalved for more rebound damping if I choose to dial more in. The 700# spring needed 16mm of preload to get 30mm of loaded sag, and Jim felt 16mm of preload is too much.

There are many variables to consider when selecting a spring rate. I once thought that you just take the rider weight and look the spring up on a chart. Done. It's not that easy.

Until you know the free and loaded sag numbers with a particular spring you can't choose a spring rate. And even then you have to test the spring and adjust preload for your riding conditions, changing spring rate if the required preload is too high or too low.

Jim Lindemann and BCM could go into this in greater detail. I'm not much of a suspension guy.


Modified by DanST4 at 6:19 AM 2/12/2005

Glad you got the right setup..Keep us posted.

The 800# spring is back on the bike and I took it for a long test ride, long for a 53F day that is.

Free sag is around 1/2". Loaded sag is around 1.25". Both measurements were taken by me, and me alone, with a yardstick laying up against the bike, so they're not all that accurate.

The ride is a little different, a bit more plush if you can believe that. A stiffer spring but a plusher ride. Less preload with the 800# spring equals a better ride I guess. Suspension setting is not my strong point, yet.

Lindemann changed the shims in the Penske shock so that I now have the ability to dial-in more rebound damping if I choose. I set it up with about the same rebound effect as before. What I do is bounce the rear of the bike up and down while adding rebound until I find the point where the rebound effect is just noticeable. I start there.

That point was at 24 clicks, now that same point is at only 16 clicks so I now have more rebound to play with.

So far the ride is controlled, plush, and with the proper free and loaded sag. When it warms up a bit I'll see how it react to mid-corner dips.

So far, so good. The 800# spring was the ticket!

Well I've had the 800# spring out back for several thousand miles now and I must say that having the correct spring rate really is the first step in setting up the suspension. You really do need to have the proper free and loaded sag. Finally I notice the difference rebound and compression settings have on the suspension action. And the ride quality is much improved over the lower-rate spring (less preload with the right spring rate).

Too bad it took me 3 years to finally go with the right rate. I just found it hard to believe that I'd need that much higher rate out back, considering that going from a 0.95kg/mm to a 1.05kg/mm up front worked so well.

Over the years I've heard of people finally giving up on aftermarket shocks because they "just couldn't get them to work". It's the spring rate, then the valving.